The error "Setup cannot find ProPlus.WW\propsww2.cab" usually isn't because the file is missing from the world, but because the installer cannot access it locally for several reasons: Corrupt Media

Missing: proplus.ww\propsww2.cab

If a previous installation failed, it might be blocking a new one. Microsoft provides a tool called "SaRA" (Support and Recovery Assistant) to completely uninstall Office traces.

The primary purpose of the "Proplus.ww\Propsww2.cab" file is to store installation files for Microsoft Office. When you download or install Office, this file acts as a container for other files needed during the installation process. It may include necessary program files, settings, and configurations specific to the Professional Plus version of Office.

As mentioned, security software often interferes with CAB extraction. Disable Real-Time Protection for 10 minutes while you finish the Office installation.

: After purchasing, you'll receive a product key or be able to sign in with your Microsoft account. Go to the Microsoft Office website, sign in, and click on the "Install" button. Choose the version you purchased (e.g., Office 365, Office 2021).